1. Field of the Disclosure
The present disclosure relates to an electrowetting display device.
2. Description of the Related Art
Photo-electrical technology has experienced rapid growth, and various displays have been rapidly developed.
The Liquavista company has developed EWDs. EWDs comprise pixels constructed by non-polarized colored oil drops, a polarized aqua solution, a hydrophobic layer and hydrophilic pixel ribs. The non-polarized oil drops are disposed on the hydrophobic layer and isolated from each other by the hydrophilic pixel ribs. The polarized aqua solution is disposed on the non-polarized oil drops. The operation principle of the EWDs is as follows. When the display is not applied a voltage, the non-polarized oil drops spread on the hydrophobic layer, so the display shows the color of the oil, and it is a dark state. When the voltage is applied, the polarized aqua solution could be attracted to the hydrophobic layer due to the electrostatic induction, and it is a bright state.
In order to comply with the requirements of the production speed, dipping is the method to the non-polarized oil. The non-polarized oil suffers from interface tension between the pixel ribs and the subsequently filled-in polarized solution, thereby, the non-polarized oil cut off by the polarized solution. The thickness of the non-polarized oil is designed as high as the height of the pixel ribs. If the display has a 75% aperture ratio, an average height of the non-polarized oil in the bright state may be four times greater than that in the dark state. In this situation, the non-polarized oil of the EWDs may overflow to adjacent pixels, causing the uniformity of the operated display to be influenced.
Various methods have been developed to improve the stability of the EWDs. Apertures of electrodes of the EWDs can be designed to divide a region of shrunk oil drops into several sub-regions, Additional ribs can be fabricated on an upper substrate of the EWDs. The upper substrate is then assembled opposite to a lower substrate to isolate adjacent pixels from each other.